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Probe to sample comet's primordial matter
Monday, June 18, 2001 By Jim Erickson, Scripps Howard News Service
A spacecraft is about to be built that will blast a football field-sized crater into a comet and dredge up ices unchanged since the birth of the solar system
Ball Aeropace of Boulder, Colo., will receive about $100 million from NASA to build the probe, called "Deep Impact."
"This is a major step for us, to put together an entire planetary spacecraft. We've never done that before," said Jerry Chodil, vice president of civil space systems at Ball Aerospace and Technology Corp.
Ball will build the spacecraft and its science instruments. Though Deep Impact is Ball's first spacecraft, the company has built more than 100 science instruments for other missions.
The probe is scheduled for launch in January 2004 and will arrive at comet Tempel 1 in 2005.
Comets are chunks of ice and dust that orbit the sun. Scientists believe these wandering ice balls contain unaltered remnants of the spinning disc of gas, dust and ice that formed the solar system 4.6 billion years ago.
Several space probes flew past comet Halley in 1986, and NASA's Stardust spacecraft is on its way to comet Wild-2, where it will gather comet dust and return it to Earth.
But Deep Impact will be the first attempt to sample the interior of a comet. The encounter should help refine theories about the formation of the sun and planets.
"We generally think that comets contain the only material that may have preserved its chemical composition from the formation of the solar system," said University of Maryland astronomer Michael F. A'Hearn, lead scientist for the mission.
Tempel 1 is about three miles across, and it orbits the sun every 51/2 years. In July 2005, as the comet approaches the sun and passes close to Earth, Deep Impact will release a 770-pound "impactor spacecraft."
Like a smart bomb, the impactor will home in on the comet and strike it at 22,300 mph. The collision is expected to blast a crater 100 yards across and 25 yards deep. Cameras and other instruments on the impactor and its mother ship will snap pictures and analyze the chemical composition of the excavated ices.
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